Puffing on Polonium

Puffing on Polonium

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Dec 4 06 6:33 PM

Puffing on Polonium

New York Times Op-Ed - December 1, 2006

By ROBERT N. PROCTOR

Stanford, Calif.

WHEN the former K.G.B. agent Alexander V. Litvinenko was found to have been poisoned by radioactive polonium 210 last week, there was one
group that must have been particularly horrified: the tobacco industry.

The industry has been aware at least since the 1960s that cigarettes contain significant levels of polonium. Exactly how it gets into
tobacco is not entirely understood, but uranium "daughter products" naturally present in soils seem to be selectively absorbed by the tobacco
plant, where they decay into radioactive polonium. High-phosphate fertilizers may worsen the problem, since uranium tends to associate with phosphates. In
1975, Philip Morris scientists wondered whether the secret to tobacco growers' longevity in the Caucasus might be that farmers there avoided phosphate
fertilizers.

How much polonium is in tobacco? In 1968, the American Tobacco Company began a secret research effort to find out. Using precision analytic
techniques, the researchers found that smokers inhale an average of about .04 picocuries of polonium 210 per cigarette. The company also found, no doubt to
its dismay, that the filters being considered to help trap the isotope were not terribly effective. (Disclosure: I've served as a witness in litigation
against the tobacco industry.)

A fraction of a trillionth of a curie (a unit of radiation named for polonium's discoverers, Marie and Pierre Curie) may not sound like
much, but remember that we're talking about a powerful radionuclide disgorging alpha particles - the most dangerous kind when it comes to lung cancer -
at a much higher rate even than the plutonium used in the bomb dropped on Nagasaki. Polonium 210 has a half life of about 138 days, making it thousands of
times more radioactive than the nuclear fuels used in early atomic bombs.

We should also recall that people smoke a lot of cigarettes - about 5.7 trillion worldwide every year, enough to make a continuous chain
from the earth to the sun and back, with enough left over for a few side-trips to Mars. If .04 picocuries of polonium are inhaled with every cigarette,
about a quarter of a curie of one of the world's most radioactive poisons is inhaled along with the tar, nicotine and cyanide of all the world's
cigarettes smoked each year. Pack-and-a-half smokers are dosed to the tune of about 300 chest X-rays.

Is it therefore really correct to say, as Britain's Health Protection Agency did this week, that the risk of having been exposed to
this substance remains low? That statement might be true for whatever particular supplies were used to poison Mr. Litvinenko, but consider also this:
London's smokers (and those Londoners exposed to secondhand smoke), taken as a group, probably inhale more polonium 210 on any given day than the
former spy ingested with his sushi.

No one knows how many people may be dying from the polonium part of tobacco. There are hundreds of toxic chemicals in cigarette smoke, and
it's hard to sort out how much one contributes compared to another - and interactive effects can be diabolical.

In a sense, it doesn't really matter. Taking one toxin out usually means increasing another - one reason "lights" don't
appear to be much safer. What few experts will dispute is the magnitude of the hazard: the World Health Organization estimates that 10 million people will
be dying annually from cigarettes by the year 2020 - a third of these in China. Cigarettes, which claimed about 100 million lives in the 20th century,
could claim close to a billion in the present century.

The tobacco industry of course doesn't like to have attention drawn to the more exotic poisons in tobacco smoke. Arsenic, cyanide and
nicotine, bad enough. But radiation? As more people learn more about the secrets hidden in the golden leaf, it may become harder for the industry to align
itself with candy and coffee - and harder to maintain, as we often hear in litigation, that the dangers of tobacco have long been "common
knowledge." I suspect that even some of our more enlightened smokers will be surprised to learn that cigarette smoke is radioactive, and that these
odd fears spilling from a poisoned K.G.B. man may be molehills compared with our really big cancer mountains.

Robert N. Proctor is a professor of the history of science at Stanford University.

The following question was answered by an expert in the appropriate field:

How much radiation dose is received by a cigarette smoker?

Interestingly, this subject was initially investigated some 40 years ago by scientists at the School of Public Health at Harvard University. Working with
physicians in the neighboring Harvard teaching hospitals, they were able to obtain lungs taken during autopsies of smokers who had died from lung cancer. The
School of Public Health scientists carefully analyzed samples from selected areas of these lungs and found that they contained relatively high concentrations
of 210Po (polonium-210), a naturally occurring radionuclide that the International Commission on Radiological Protection considers to be one of
the most hazardous of all radioactive materials. In fact, it is far more hazardous than 239Pu (plutonium-239). Of particular significance was that
the Harvard studies showed that this radionuclide tended to concentrate in "hot spots" at bifurcations of segmental bronchi within the lungs,
precisely the areas where lung cancer originates among cigarette smokers.

Armed with this information, studies were conducted to determine the source of the 210Po. Although the initial assumption was that it was taken
up by the tobacco plant from the soil, the investigations revealed that it was deposited on the leaves of the plants (which are large and sticky) from the
air. Just as the decay of naturally occurring radium in the soil often results in the presence of relatively high concentrations of radon and its radioactive
decay products in the air inside buildings, the decay of radium in the soil outdoors results in the presence of radon and its decay products in the
surrounding air. Whereas radon is a gas, its radioactive decay products are solids. Enhancing the adherence of these decay products to the tobacco leaves is
the fact that they are electrically charged and readily adhere to any surface with which they come into contact. When a smoker lights a cigarette, the
210Po is volatilized and, when he/she inhales, it is deposited in the lungs.

Based on careful assessments of the concentrations of 210Po in the lung tissues, it was estimated that the "hot spots" received an
annual dose of about 160 millisievert (about 16,000 millirem), two of the more common units for expressing doses from ionizing radiation. To provide
perspective, it is useful to compare this dose to the limit stipulated, for example, by the US Environmental Protection Agency for members of the US public.
Making this difficult in this case, however, is that the annual dose limit for members of the public (1 millisievert, or 100 millirem) is expressed in terms
of a dose to the whole body, whereas, as noted above, the dose to a smoker is limited to a very small portion of the body.

Nonetheless, in a report published in 1987, the National Council on Radiation Protection and Measurements (NCRP 1987) sought to make such a comparison,
the tentative outcome of which suggested that the annual dose to a smoker (when converted into an equivalent dose to the whole body) was more than 10 times
the annual dose limit for a member of the public. Having provided this estimate, however, the NCRP went on to state that they would prefer not to make such a
comparison. That is to say, the comparison to the annual whole-body dose limit may not be completely valid.

In a similar manner, the scientists at Harvard, while acknowledging that the dose to a smoker was high, were quick to recognize that 210Po was
only one of a multitude of carcinogenic compounds in cigarettes. For this reason, they were hesitant to cite 210Po as a primary source of lung
cancer among cigarette smokers. Based on these considerations, their conclusion was that "we believe 210Po may be an important factor in the
initiation of bronchial carcinoma in humans" (Little et al. 1965).

Luckily Alpha Particles released by the radioactive decay of Polonium 210 can only hurt you if you ingest or inhale them.

From my radiation safety manual:

"(Alpha particles) are not considered an external radiation hazard to living systems because they do not penetrate very deeply....However, if
radioactive atoms that emit alpha particles are allowed to enter the body (such as through the lung), they can present a significant radiation hazard. They
generally have long half-lives and have long residence times in the body which results in very high doses to the cells immediately surrounding the
radioactive particle. Extreme care should be taken to avoid inhalation of alpha particles."

Tobacco firms kept quiet on polonium role in cigarettes

Some of the world's biggest tobacco firms researched the lethal radioactive substance polonium - present in cigarettes - over a 40-year period but
never published the results, according to a new scientific article.

Experts have examined more than 1,500 internal documents from tobacco companies.

Polonium 210 is known to cause lung cancers in animals and studies suggest it is responsible for 1 per cent of all lung cancers - equivalent to 11,700
deaths globally - each year in the US.

It is also the substance that poisoned the Russian dissident Alexander Litvinenko in London in 2006.

Yet tobacco companies, while attempting but failing to remove the substance from their products, have kept quiet about their research, experts say.

One of the documents - all of which were made public through legal actions - said publication would be "waking a sleeping giant". The authors of
the article, published in the September edition of American Journal of Public Health, also say tobacco companies feared possible litigation.

The quoted studies show polonium is present on the tobacco leaf and inside it as part of its chemical make-up. Tobacco company scientists spent years
trying to remove the substance by washing the leaf, achieving only partial success. Attempts at genetic modification and creating filters to remove it also
failed.

The research article, led by Monique Muggli, from the Mayo Clinic in Minnesota, says: "Philip Morris documents show the majority of the company's
internal reports regarding PO-210 [Polonium 210] were not published. One manuscript believed by some Philip Morris scientists to be favourable to the tobacco
industry was withheld from publication for fear of heightening public awareness of PO-210."

It then quotes an internal document that says publication of that research, from 1978, "has the potential to wake a sleeping giant".

Ms Muggli added that, while tobacco companies tried to obscure other health controversies, their line on polonium seemed to be simply not to raise the
issue.

"Unlike other smoking and health issues, where the industry line was to create doubt, in relation to polonium 210 and the radioactivity of
cigarettes, the companies wanted to hide from that issue publicly. They continue to minimise the recognition of radioactivity in their products in smoking
and health litigation," she said.

A spokeswoman for British American Tobacco said it was not known which constituents of cigarette smoke caused cancer and argued that polonium 210 is also
present in food.

"It's fairly common knowledge polonium 210 is in cigarette smoke because it's present in all such plant types, including strawberries,"
she said. "There was a 1977 study that found, of the daily intake of the polonium 210 in a smoker, 77.3 per cent came from food and 17 per cent from
tobacco. The World Health Organisation is trying to determine which constituents of tobacco smoke are most important in diseases including lung cancer, but
as yet have not concluded polonium 210 is a priority constituent."

A spokesman for Philip Morris said many reports into polonium and cigarette smoke had been published over the last 30 years and links were available on
their website. He added that Philip Morris had published some of its research but no company would publish all its internal findings.